Dataplot: Sizing

Dataplot uses a percentage coordinate scale. That is, it divides
the screen into a 0 to 100 scale in both the horizontal and
vertical directions. If you use either the
MULTIPLOT command or the
WINDOW COORDINATES command,
this defines a subset of the screen to be used by the next plot.
Dataplot defines a new 0 to 100 scale for this sub-plot area.
In this case, the percent sizes are relative to this sub-plot area,
not the full screen.

Sizes in Percentage Scale

Sizes in Dataplot are specified in terms of this 0 to 100 scale.
For example, the command TITLE SIZE 3 sets the height to 3% of the
vertical size of the output device.

Sizes by Character Height

In most cases, sizes are specified by the specifying the height
of the character. Dataplot then automatically sets the width
to be half the size of the height. That is, a TITLE SIZE 3 command
sets the height of the character to be 3% of the vertical size of
the output device and the width of the character to be 1.5% of the
width of the output device.

Sometimes Desirable to Set Character Width Explicitly

In some case, it is desirable to be able to set the width of the
character explicitly. This is particularly true when using the
MULTIPLOT or WINDOW COORDINATES commands. In these cases, it
is possible for the ratio between the height and width of the
sub-plot area to be different enough that it drastically distorts
the appearance of the character. The table below gives some
commands that allow you to specify both the height and width of
the character.

The default size for all plot elements is 2. That is, the
height of the character is set to 2% of the vertical size of the
graphics device and the width is set to 1% of the width of the
graphics device.

In setting sizes, there is a distinction between the use of
hardware generated characters and software generated characters.
The FONT command is used to
specify whether hardware or one of seven different software
characters are used. The default is to use hardware characters.

Software Characters

Software characters are drawn by Dataplot as a sequence of moves
and draws. Their appearance should be consistent across different
output devices (subject to the different resolutions of output
devices).

Hardware Characters

Hardware characters use the character generating mechanism of
that device. This means that the appearance of hardware characters
can vary, sometimes substantially, across different graphics
devices. For example, Postscript provides for scalable, typeset
quality characters in 35+ different fonts. On the other hand, the
Tektronix device provides only 4 discrete character sizes with a
comparatively low quality appearance. Hardware characters,
especially for screen devices, tend to be significantly faster
to draw than software characters.

Hardware Characters Often Have Fixed Width

Note that hardware characters also typically fix the width of the
character relative to the height. In general, this ratio cannot
be changed. This means that the various Dataplot commands that
allow you to specify the width independently of the height do
not have any effect on hardware characters. Fortunately, the
primary reason for wanting to do this, i.e. to correct for
distortions resulting from the use of the MULTIPLOT or WINDOW
COORDINATES commands, do not apply in this case either.

Hardware Characters May Have Limited Number of Available Sizes

If you change the size of a character and that size is not
reflected on the particular device, this probably means that
you are using hardware characters on a device with a limited
number of sizes (some only support a single size). The
documentation for the various
output devices indicates
how many sizes the output device supports.

DEVICE FONT Command

The command DEVICE <1/2/3>FONT can be used to specify
whether the hardware font or a software font is used on a specific
device. The most common use of this command is to set a software
device for the screen (DEVICE 1), where the hardware fonts might be
limited and poor quality, while still preserving the use of hardware
characters for a Postscript output device (DEVICE 2). To do this,
you could enter the following command: